Weighing control system



May 14, 1963 Filed Jan. 5, 1962 s. c. HARRIS, JR. ErAL 3,089,555

WEIGHING CONTROL SYSTEM 2 Sheets-Sheet 2 use nun. seunce 10 M f s OUTPUT FIGURE 20.

MECHANICAL DRIVE 29 mcnusz TARE uuu.

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k f w I FOUND 02cm: :0 POUND DECADE I00 POUND DECADE 1 z 4 a lo 20 40 80 I00 200 400 FF FF FF FF FF FF FF FF FF FF FF FF I000 500 250 125,; mg, sagas |z.a w, s, 2.: 1.2g a n nn Rana nnn"n FIGURE 25 SAMUEL c. HARRIS, JR.

LAWRENCEJ. LANGLEY BY Wren United States Patent Ofifice 3,989,555 Patented May 14, 1963 The invention relates to a weighing control system, and particularly to a weighing control system for controlling material as it is being supplied so as to provide the desired weight of material.

The present manufacture of certain products, for example refractory materials such as firebrick, has reached a fairly high degree of refinement despite such manufacture under mass production or mass quantity techniques. The ditterent basic ingredients which make up the final product must be carefully and accurately measured so that the final product has the desired properties or characteristics. Such measurements are usually made by weight.

Accordingly, an object of the invention is to provide a novel weighing control system for controlling a material as it is being supplied.

Another object of the invention is to provide a novel weighing control system which accurately controls the weight of material being supplied and which may provide for any tare weight which may be present.

Another object of the invention is to provide a novel weighing control system which accurately controls the weight of material being supplied and which may measure and indicate the weight of material which has been supplied.

In addition to requiring careful and accurate weighing of material or ingredients, present manufacture may require a large number of different basic ingredients in the final product. At present, it is not unusual for a product to require a mixture of material which weighs hundreds of pounds and which may have any number of different ingredients ranging in amounts from one pound to hundreds of pounds. Such a range of weights and different ingredients results in difficult conditions for a weighing control system.

Therefore another object of the invention is to provide a weighing control system which controls the weight of material being supplied and which permits each ingredient to be supplied at a bulk rate and/or at a trickle rate.

In accordance with the invention, a command signal source and a weight signal source are provided, the command source providing a signal indicative of the desired weight of material and the weight source providing a signal indicative of the weight of material supplied. A common junction is coupled to both sources, and means are coupled to the common junction for providing a control signal which is indicative of the relative values of the two signals. If the command signal bears one relation to the weight signal, a control signal is produced which indicates that an additional weight of material should be supplied; if the command signal bears a different relation to the weight signal, a control signal is produced which indicates that the desired weight of material has been supplied. A tare null source may be coupled to the common junction to provide or compensate for any tare weight present in the receptacle for the material being sup-plied. Also, a bulk weight ofiset source may be coupled to the common junction to provide or make allowance for supplying some material at a trickle rate after all but a predetermined weight of material has been supplied at a bulk rate. Also, the weight of material which has been supplied may be measured if desired.

The invention will be better understood from the following description given in connection with the accompanying drawing, and its scope will be pointed out in the claims. In the drawing:

FIGURE 1 shows a block diagram of a preferred embodiment of a weighing control system in accordance with the invention; and

FIGURES 2a and 21) show more detailed diagrams of certain portions of the block diagram of FIGURE 1.

System Description The embodiment shown in FIGURE 1 contemplates a weighing control system for use with one source of material and with one weight measuring device or indicator. However, it is to be understood that where there are a plurality of sources of material, a number of comparable systems may be used or a single system may be used in connection with some movable receiver or receptacle such as a loading car which carries the control system and which is moved from source to source. In the embodiment of FIGURE 1, it has been assumed that weights of material between one pound and 999 pounds inclusive may be programed or called for, although other ranges of weights (including fractional parts of a pound) may be provided for. The control system can be used in any application which can weigh the material and provide a signal indicative of the smallest weight increment desired and which can supply the material at the desired rate. The embodiment shown in FIGURE 1 includes four signal sources: an optional tare null source 10, a command source 12, a weight measure source 14, and an optional bulk offset source 16. Each of these sources 10, 12, 14, 16 supplies a signal of a given value or magnitude and characteristic or polarity to a common junction or summing point 20. It is preferred that this signal be a current signal having a magnitude indicative of or proportional to the intelligence it represents and having either a plus or a minus polarity or direction (as indicated) relative to a point of reference potential such as ground. Preferred embodiments of the tare null source It! and the command source 12 are shown in greater detail in FIG- URES 2a and 2b of the drawing.

The tare null source 10, which is optional, provides a positive current which is supplied by a source of direct current potential 24 connected to a potentiometer or variable resistor 26 as shown in FiGURE 2a. The negative terminal of the source of potential 24 is connected to ground. A slider or contact 28 engages the potentiometer 26 and provides the positive current output as indicated. The position of the slider 28 determines the amount of positive current so provided. This position is attained or changed in accordance with some suitable mechanical drive 29 which is activated in either of two directions by appropriate increasing tare null signals or decreasing tare null signals provided by the leads shown in FIGURE 1.

The command source 12 provides a positive current having a value or magnitude indicative of the desired weight of material which is to be provided. The system shown in FIGURE 1 has been assumed to control weights between 0 and 999 pounds in increments of one pound. As shown in FIGURE 2b, the command source 12 has been provided with three decades, one representing 0 to 9 increments of one pound. one representing 0 to 9 increments of ten pounds, and one representing 0 to 9 increments of pounds. Each decade includes four binary flip-flops (or bistable multivibrators) and four associated respective weighting resistors which can be energized with preferably equal voltages. Such devices or their equivalent are known in the art. All of the weighting resistors are coupled at one end to a common output bus. These Weighting resistors have the relative magnitudes (based on a resistance R which, for a certain voltage, would allow a current representing 1000 pounds to flow) as indicated in FIGURE 2b. The state of the flipflops is determined by the input (preferably programed and supplied from a suitable source not shown) which is applied to the flip-flops. A flip-flop in the set state energizes its weighting resistor, and a flip-flop in the reset state deenergizes its weighting resistor. The magnitude of the weighting resistors determines the quantity or magnitude of current so provided. For the purposes of illustration at this point and subsequently, it is assumed that a weight of 861 pounds is to be provided or supplied. If a command current indicating a weight of 861 pounds is to be provided, the 801) flip-flop is set to energize its weighting resistor 125R in the 100 pound decade, the 40 and 20 flip-flops are set to energize their weighting resistors 25R and 50R in the ten pound decade, and the 1 flip-flop is set to energize its weighting resistor 1000R in the one pound decade. If equal voltages are provided for the weighting resistors, the resistors provide currents inversely proportional to their magnitudes. If the voltage supplied on energization is ten volts and if R is equal to ten ohms, it will be seen that the weighting resistor 1.25R provides a current of 800 milliamperes, the weighting resistors 25R and 50R provide 40 and 20 milliamperes respectively, and the weighting resistor 1000R provides 1 milliampere, this being a total of 861 milliamperes.

The weight measuring source 14 may be any weightto-electrical-signal transducer which is suitable, such devices being known in the art and generally referred to as load cells. The weight measuring source 14 provides a negative-going current which increases in magnitude (in a negative direction) with increased Weight. The weight measuring source 14 is appropriately coupled to the receiver or receptacle of material so that its output or negative current reflects the weight of the receptacle and the material supplied to it. Such a device has not been illustrated since it is known in the art and the description given with such a known device is considered adequate. Likewise, no detailed diagram of the optional bulk offset source 16 has been given. This source 16 is also a source of negative current which can be set at any predetermined fixed magnitude. The bulk offset source 16 is provided for subtracting a portion of the positive command current and thus reserving, in effect, some predetermined amount of weight so that this predetermined amount of weight may be supplied at a different rate, preferably a trickle or a slow rate as opposed to a bulk rate. The bulk offset source 16 is arranged to be in either an off or an on condition in response to appropriate signals, thus either providing no current or providing its predetermined current. Since the command source 12 has been exemplified as providing one milliampere per pound of desired weight, the other sources are likewise arranged to provide a positive or negative current, as the case may be, of one milliampere per pound of weight to be indicated.

The junction point 20 is coupled to the input of a control signal generator 22 which may be a high gain amplifier having a clipped output which is preferably only positive-going. It is to be noted that the common junction point 20 permits each of the sources 10, 12, 14, 16 to be coupled directly to the generator 22 Without any amplification. The output of the generator 22 is clipped and is made positive-going for use in logic circuitry. The generator 22 has an input impedance 23 coupled between the junction point 20 and ground. Under basic electrical laws, all of the currents flowing toward or into the junction point 20 must equal all of the currents flowing away from or out of the junction point 20. If the algebraic sum of the currents provided by the sources 10, 12, 14, 16 does not equal zero, the inequality or difference is re ilected or indicated by a current flow through the input impedance 23 of the control signal generator 22. Thus, if the sum of the positive currents from the sources 10, 12 is greater than the sum of the negative currents provided by the sources 14, 16, a positive current flows from the junction point 20 through the input impedance 23 of the control signal generator to ground. This will hereinafter be referred to as a positive input signal. However, if the negative currents provided by the sources 14, 16 exceed the positive currents provided by the sources 10, 12, a negative current then flows from ground through the input impedance 23 of the control signal generator 22 to the junction point 20. This will hereinafter he referred to as a negative input signal. The input signals applied to the control signal generator 20 are amplified and clipped as mentioned. If a positive input signal is applied to the control signal generator 22, a positive output is provided by the generator 22, this positive output being hereinafter referred to as a logic 1 output. If, however, a negative input signal is applied to the control signal generator 22, no voltage output, hereinafter referred to as a logic 0, is provided by the control signal generator 22. This is indicated by the legends at the output of the generator 22. The generator 22 may have some finite deadband in which it is insensitive to a change of current and input signal. This deadband depends on a number of factors not pertinent here. In a practical embodiment of a generator, this deadband may correspond to a current A of one-tenth of a milliampere. Thus, where one milliampere of current represents one pound of weight, an error of one-tenth pound may result from the deadband current A. A smaller deadband and a corresponding smaller deadband current A may be attained by appropriate circuit design. However, other circuit errors, such as the resolution of the weight measuring source 14, may not justify providing a smaller deadband.

The output from the control signal generator 22 is aplied to three AND gates 30, 34, 36. All of the gates shown in FIGURE 1 are AND gates. An AND gate is known in the art and requires that all of its inputs meet a certain condtion before providing a certain output condition. For the purposes of explanation, it has been assumed that each of the AND gates shown requires that all of its inputs be at logic 1 to produce a logic 1 at its output. The output of the control signal generator 22 may also be applied to a weight register scanner 40 which can be used if desired to control the command source 12 when the weight of material supplied is to be measured. The output of the control signal generator 22 is also applied to an inverter 42, this inverter 42 merely inverting the output of the generator 22 in terms of logic. If the output of the generator 22 is a logic 1, the output of the inverter 42 is a logic 0. If the output of the generator 22 is a logic 0, the output of the inverter 42 is a logic 1. The output of the inverter 42 is applied to three AND gates 32, 44, 46. The gates 30, 32 provide increase or decrease signals for the tare null source 10 depending upon which of the gates 30, 32 produces a logic 1. A null tare input signal is provided to the gates 30, 32 during the time the tare is to be nulled out. A draw material input signal is provided for the gates 34, 36, 46 to provide these gates with a logic 1 input when it is desired that material be drawn from its source and supplied to a receptacle or receiver. A bulk-trickle flip-flop 50 (bistable multivibrator) is provided, this fiip-fiop 50 taking one of two conditions depending upon whether a bulk set signal or a trickle set signal is provided. If a bulk set signal is applied to the flip fiop 50, the flip-flop 50 provides a logic 1 at the AND gate 34 and a logic 0 at the AND gates 36, 44. If a trickle set signal is applied to the flip-flop 50, the flip-flop 50 provides a logic 1 at the AND gates 36, 44 and a logic 0 at the AND gate 34. The output of the AND gate 44 produces or provides a cycle complete output signal. The output of the AND gate 46 is used to turn off the bulk offset source 16 and at the same time to provide a trickle set signal to the flip-flop 50. A start cycle input signal is provided to turn on the bulk offset source 16 and to provide a bulk set signal to the flip-flop 50. The output from the AND gate 34 is used to control a bulk gate, this bulk gate being J some suitable mechanism which permits material to be supplied or drawn from its source at a bulk rate. The output of the AND gate 36 is used to control a trickle gate, this trickle gate being some suitable mechanism remains, and the decrease tare null signal continues. Then, a tare null positive current of 33 minus A milliamperes is provided. At this point, a net negative current of A milliarnpere is provided to the input of the conwhich permits material to be supplied or drawn from the trol signal generator 22. The output of the control signal source at a trickle rate. These gates may be electrogenerator '22 then becomes a logic 0. At this point, it magnetically operated trap doors of a bulk size and a would be appropriate to remove the null tare input signal trickle size, such doors permitting material to flow from to prevent further hunting or oscillation. Such removal the source at either a bulk rate or at a trickle rate into a can be effected by the transition from a logic 1 to a logic car or receiver or receptacle. A dashed line is shown 0 at the output of the generator 22, or by other suitable between the bulk and trickle gates and the weight measure means. In the second illustration, a negative current source 14. This dashed line is intended to indicate that 33 milliarnperes is provided by the weight measure source as the gates are opened to permit material to be supplied 14, a positive current of 20 milliamperes is provided by to a receptacle, the weight measure source 14 is operated the tare null source 10 from a prior situation, no current accordingly with the added weight of material so supplied. is provided by the command source 12 and the bulk oil S t 0 set source 16, and thus a net negative current of 13 min!- ys em per amperes milliamperes minus 33 milliamperes) is pro- The operation of the weighing control system will now vided to the input of the control signal generator 22. be described and explained in terms of a specific example. This net negative current of i3 milliamperes causes the This example is set out in the following table: 20 control signal generator 22 to provide a logic 0 at its Total Wt. Tare Null Corn- Bulk Otl- Generator Generator Step or Operation Wt. Mons. Source nmnd set Source Input Logic Present Source Current Source Current Current Output Current Current Measure taro 33 33 +50 0 0 +17 1 as -s3 +33 0 n 0 1 Tareonfpllod out 33 -33 +33- 0 0 A 0 Measure tare. 33 --33 +20 0 0 -13 0 s3 -s3 +33 0 0 0 l Tare nulled out 33 -33 +33A 0 0 --A 0 Start cyclebulk draw 33 33 +33A +861 25 +836-A 1 After 5001!]5. drnwn.- 533 533 +33-A +861 25 +336A l Alter 8351135 dravm 868 -868 +33-A +861 25 +1-A 1 After 8361135. drawn 869 869 +33-A +861 -25 A 9 Stop bulk draw. Start trickle drawn-.. S69 -8fi9 -l33-A +861 0 +25-A 1 After 860 lbs. drawn. 893 893 +33A +861 0 +1-A 1 After 861 lbs. draurm 894 8Q4 +33-A +861 0 A G In this example, it has been assumed that a weight of 861 output. A logic 1 is now provided at the input of the pounds is to be provided, that the tare weight of the gates 30, 32 by a null tare signal applied to the null tare receptacle is 33 pounds, that the bulk olfset weight is 25 input. Since the control signal generator is producing 2 pounds, and that the generator 22 has an indeterminate logic 0 output, and since the inverter 42 changes this to a logic output for input currents from zero to minus A logic 1, the AND gate 32 provides a logic 1 output which milliarnpere. Before the command source current is provides a signal which increases the tare null. The AND applied to the junction point 20, the tare of 33 pounds gate 30 has a logic 0 applied to it directly from the genmay be nulled out or eliminated. This is done by erator 22 and therefore produces a logic 0 output. This weighing the receptacle and any tare by the weight 45 increase tare null signal causes the potentiometer arm measure source 14 and comparing its current with what- 28 (in FIGURE 2a) to move upward until a positive ever current is being provided by the tare null source 10. current of 33 milliamperes is provided. The net current When the receptacle and tare are weighed, the tare null to the generator 22 becomes zero so that its output besource 10 may be in the condition of providing a current comes a logic 1. This logic 1 combined in the AND equivalent to more or less than a weight of 33 pounds gate 30 causes a logic 1 output which provides a signal as a result of a previously different tare weight. For which decreases the tare null. This causes the potenillustrative purposes, two previous conditions have been tiometer arm 28 to move downward until a positive curassumed, these being a previous tare weight of 50 pounds rent of 33 minus A milliamperes is provided. At this or a previous tare weight of 20 pounds. In the first point, a net negative current of A milliampere is provided illustration, a negative current of 33 milliamperes is proto the input of the control signal generator 22, and its outvided by the weight measure source 14, a positive curput becomes a logic 0. If the transition from a logic 1 rent of 50 milliamperes is provided by the tare null to a logic 0 at the output of the generator 22 is utilized source 10 from a prior situation, no current is provided as in the other tare example, the null tare input signal by the command source 12 and the bulk offset our e 16, may he removed to prevent further hunting or oscillation. and thus a net positive current of 17 milliamperes (50 The bulk Olfsfit Source 16 has bfieh assumfid t0 P milliamperes minus 33 milliamperes) is provided to the vide a negative offset current of 25 milliarnperes which input of the control signal generator 22. This net posicorresponds to 25 pounds. Other values may be used. tive current of 17 milliamperes causes the control signal After the fare has been finned, the Command 8011116 12 generator 22 to provide a logic 1 at its output. A logic 1 is energized so it provides a positive current of 861 milliis now provided at the input of the gates 30, 32 by a null 55 percs (corresponding to the desired 861 pounds) as tare signal applied to the null tare input. Since the con already dflscfihed, and the bulk OiTSeI Source 16 is turn trol signal generator 22 is producing a logic 1 output, the Oh y a Signal pp 10 its Start y l i p t 50 it provides AND gate 30 provides a logic 1 output which provides a negative current of 25 milliamperes. A negative cura signal which decreases the tare null. The AND gate 32 rent of 33 milhampel'es i5 Provided y Ihfi Weight measure has a logic 0 applied to it by the inverter 42 and there- Source 14 and a Positive current of 33 minus A millifore produces a logic 0 output. This decrease tare null p i5 Provided y the tare hull SOUTCE 0. Thus a signal causes the potentiometer arm 28 (in FIGURE 2a) net positive current of 836 minus A milliamperes (861 to move downward. When a positive current of 33 millimiih'BmPeI'BS, P1115 33 minus A milh'amperes, minus 25 amperes is provided, the net current to the generator 22 milliamperes, minus 33 milliamperes) is provided to the is zero. However the logic 1 output of the generator 22 7 input of the control signal generator 22. This is shown in the table. This current provides a logic 1 at the output of the control signal generator 22 and to the AND gates 34, 36. The start cycle input signal previously provided a bulk set signal for the bulk-trickle flip-flop 50 so that it supplies a logic 1 to the AND gate 34. When it is desired for the material to be supplied or drawn, a logic 1 signal is supplied to the AND gates 34, 36 by the application of a signal at the draw material input. At this time the AND gate 34 provides a logic 1 output signal which opens the bulk gate. The AND gate 36 does not provide a logic 1 output signal because the bulk-trickle flip-flop 50 is supplying it with a logic 0. Material is then supplied to the receptacle at a bulk rate. As it is, the weight measuring source 14 supplies increasing negative current. The various currents and the generator logic output are shown in the table after 500 pounds have been drawn. After 835 pounds of material have been drawn, a net positive current of one minus A milliampere is provided to the generator 22 so that it still produces a logic 1 which still permits material to be drawn at the bulk rate. However, as soon as 836 pounds of material have been drawn, a net negative current of A milliampere is provided to the generator 22 so that it now produces a logic output.

With the output of the control signal generator 22 now at a logic 0, the AND gate 34 immediately produces a logic 0 at its output which closes the bulk gate and stops the drawing of material at a bulk rate. The inverter 42 now provides a logic 1 at its output in response to the logic 0 input, and this logic 1, along with the logic 1 supplied by the draw material input, causes the AND gate 46 to provide a logic 1 at its output. This logic 1 turns otf the 25 milliamperes of negative current from the bulk offset source 16 and also provides a trickle set signal to the bulk-trickle flip-flop 50. This causes a logic 1 to be provided by the bulk-trickle fiipfiop 50 to the AND gate 36, and a logic 0 to be provided to the AND gate 34. When the bulk-trickle flip-flop 50 provides a logic 1 to the AND gate 36, it also provides a logic 1 to the AND gate 44. This logic 1 with the logic 1 from the inverter 42 produces a logic 1 at the output of the AND gate 44 to provide a cycle complete signal. However this is only momentary as will be explained below. As soon as the bulk offset source 16 is turned off, there is again a net positive current (25 minus A milliamperes) supplied to the control signal generator 22. The generator 22 immediately produces a logic 1 at its output again. The output of the inverter 42 becomes a logic 0 which results in a logic 0 output at the AND gate 44. Thus the cycle complete signal is removed. If this signal is to be used as a function or indication, a suitable time delay circuit may be used to prevent a momentary false function or indication. The bulk gate is kept closed because the bulk-trickle fiip-fiop 50 is now applying a logic 0 to the AND gate 34. The AND gate 36 is now provided with a logic 1 at each of its inputs and so produces a logic I at its output. This causes operation or opening of the trickle gate so that additional material is drawn at a trickle rate. After 860 pounds of material have been supplied, a net positive current of one minus A milliampere is provided to the generator 22 so that it still produces a logic 1 which still permits material to be drawn at the trickle rate. However, as soon as 861 pounds of material have been supplied, .a net negative current of A milliampere is provided to the generator 22 so that it now produces a logic 0 at its output. The logic 0 at the output of the control signal generator 22 causes the AND gate 36 to produce a logic 0 at its output and then turn off the trickle gate. The inverter 42 produces a logic 1 at its output and this logic 1, along with the logic 1 supplied by the bulk-trickle flip flop 50, causes the AND gate 44 to produce a logic 1 at its output indicating that the cycle is complete. While this is a stable condition, the draw material signal may be removed to provide a more stable condition which is changed only by external signals calling for a new cycle and a new draw.

It will be seen that the circuit or the system just described permits accurate control and measuring of the weight while the material is being supplied. Further, the system requires only one comparison element or control generator to produce the output control signal in response to any number of input signals which are needed or desired to infiuence or affect the control signal. There is no inherent error caused by generator input currents from zero to minus A milliampere because tare nulling and material drawing are performed in the same sense. That is, the extra tare null current A cancels the balance current A required in drawing. If circumstances justify, the accuracy of the 'control system may be increased by providing additional command signals and corresponding flip-flops which measure smaller increments of weight, for example, tenths, hundredths, and thousandths of a pound. Thus, the first thousandth of a pound in excess of the required amount would cause the control signal generator 22 to produce a logic 0 output that ends the cycle.

After the material has been drawn or supplied, the control system can be used to measure the actual weight of the material drawn. This is accomplished by the optional weight register scanner 40 which is coupled to the flip-flops of the command source 12 and which is rendered operative by a weight measure input signal. The weight register scanner 40 is, in effect, a programing device which first resets all of the flip-flops back to zero and deenergizes the weighting resistors so that the command source 12 produces no output current. The weight register scanner 40 then scans or sets each of the flip-flops to energize its respective weighting resistor beginning with the most significant (the 800 flip-flop), and continues sequentially through the other flip-flops of descending significance and ends with the least significant (the 1 flip flop). Whether a particular flip-flop is kept set (and its weighting resistor energized) depends upon the measure weight feedback signal derived from the output of the control signal generator 22. A logic 0 output keeps the flip-flop set, but a logic 1 output resets the flipflop. In the example above, 861 pounds of material and 33 pounds of tare are present. The tare null source 10 provides a positive current of 33 minus A milliamperes. So the weight register scanner 40 must only weigh the 861 pounds which is indicated by the negative current of 861 milliamperes provided by the weight measure source 14. When the 800 flip-flop is set, it provides a positive current of 800 milliamperes which leaves a net negative current of 61 milliamperes applied to the generator 22. The generator 22 produces a logic 0 output which is applied to the weight register scanner 40. The scanner 40 keeps the 800 flip-flop set in response to the logic 0. The scanner 40 then sets the 400 flip-flop, this resulting in a net positive current of 339 milliamperes. A logic 1 is produced by the generator 22 in response to this positive current, this logic 1 causing the scanner 40 to reset the 400 flip-flop. The remaining flip-flops are likewise set in sequential fashion, with the 40 flip-flop and the 20 flip-flop being kept set. At this point a positive current of 860 milliamperes is provided by the command source 12, and this results in a net negative current of 1 milliampere. Setting of the 8, 4, and 2 flip-flops results in a net positive current and a logic 1 which results in these flip-flops being reset. The l flip-flop is then set and a positive current of 861 milliamperes is provided resulting in a net current of zero. The generator 22 does not change its logic 0 output so that the 1 flip-flop stays set. Setting of the 1 flip-flop can be used to halt the weight measure cycle. Setting of the flip-flops (in this example the 800, 40, 20, and 1 flip-flops) can be indicated in some way (such as lights) to provide an indication of the measured weight. If the weight being measured had been 800 pounds instead of 861 pounds, the 800 flip-flop would have been set. This would result in a net current of zero, but the generator 22 would still provide its logic output (resulting from the net negative current prior to setting of the 806 flip-flop) so that the 800 flip-flop is kept set. All settings of the subsequent flip-hops would result in a net positive current and this would result in a logic 1 output that would reset these ilip-fiops. After the l flip-flop is set and reset, the weight measure cycle would end.

It will be seen that the weighing control system of the invention provides a new and novel means for controling the weight of material supplied. This system incorporates electronic circuitry which provides improved and accurate operation which has not been previously attainahlc. It is to be understood that modifications or changes may be made without departing from the scope of the invention. For example, the tare null source 19 is not essential if the "ire weight can be neglected. Likewise, the bulk offset source is not essential if drawing at a bull: rate is satisfactory or if drawing at any single rate (either bull; or trickle or somewhere in between) is permissible. Measuring the weight or" the drawing material is also optional. Other modifications may be made by persons skilled in the art without departing from the spirit of the invention or from th scope of the claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A system for controlling the weight of material supplied at a bulk rate and at a trickle rate from a. source to a receiver comprising a command source for producing a first polarity of current having a magnitude proportional to the desired weight of material, a weight source coupled to said receiver for producing a second and opposite polarity of current having a magnitude proportional to the weight of material supplied to said receiver, a tare source for producing a current having said first polarity and having a variable magnitude, an offset source for producing a current having said second polarity and having a magnitude proportional to the weight of material to be supplied at said trickle rate, means selectively energizing said offset source, a common summing junction coupled to said command, weight, tare, and oilset sources, means coupled to said junction for producing a control signal indicative of the relative magnitudes of said currents, means coupled to said producing means and to said tare source for changing said tare current to a magnitude proportional to the tare Weight of said receiver, means coupled to said producing means and to said material source for supplying said material at said bulk rate in response to the magnitude of said first polarity currents exceeding the magnitude of said second polarity currents, means coupled to said pro dueing means and to said offset source for removing said offset current in response to the magnitude of said second polarity currents exceeding the magnitude of said first polarity currents, and means coupled to said producing means and to said material source for supplying said material at said trickle rate in response to the removal of said offset current and in response to the magnitude of said first polarity currents exceeding the magnitude of said second polarity current.

2. The system defined in claim 1 and further comprising scanning means for causing said command source to sequentially produce currents indicative of weights beginning with the most significant weight, means coupling said producing means to said scanning means for mainaining said produced currents in response to the magnitude or" said second polarity current exceeding the magnitude of said first polarity currents, and means coupled to said scanning means for indicating said maintained currents.

3. A system for controlling the Weight of material supplied at a first rate and at a second rate comprising a command source for producing a signal having a first characteristic and being indicative of the desired Weight of material, a weight source for producing a signal having a second characteristic and being indicative of the weight of material supplied, an offset source for producing a signal having said second characteristic and being indicative of the Weight of material to be supplied at said second rate, means coupled to said command, weight, and offset sources for alternatively producing a first or a second control signal in response to said command, weight, and offset signals, means coupled to said producing means and adapted to supply said material at said first rate in response to said first control signal, means coupled to said producing means and adapted to supply said material at said second rate in response to said second control signal, and means coupled to said command source for causing said command source to provide a sequence of signals for indicating the Weight of material supplied.

4. A system for controlling the weight of material supplied at a first rate and at a second rate from a source to a receiver comprising a command source for producing a first polarity of current having a magnitude proportional to the desired weight of material, a weight source coupled to said receiver for producing a second and opposite polarity of current having a magnitude proportional to the weight of material supplied to said receiver, an offset source for producing a current having said second polarity and having a magnitude proportional to the weight of material to be supplied at said second rate, a common summing junction coupled to said command, weight, and offset sources, means coupled to said junction for producing a control signal indicative of the relative magnitudes of said currents, means coupled to said producing means and to said material source for supplying said material at said first rate in response to the magnitude of said first polarity current exceeding the magnitude of said second polarity currents, means coupled to said producing means and so to said offset source for removing said offset current in response to the magnitude of said second polarity currents exceeding the magnitude of said first polarity current, means coupled to said producing means and to said material source for supplying said material at said second rate in response to the removal of said offset current and in response to the magnitude of said first polarity current exceeding the magnitude of said second polarity current, and means coupled to said command source for causing said command source to provide a sequence of currents and to maintain certain of said currents in response to said producing means, said maintained currents indicating the weight of material supplied.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A SYSTEM FOR CONTROLLING THE WEIGHT OF MATERIAL SUPPLIED AT A BULK RATE AND AT A TRICKLE RATE FROM A SOURCE TO A RECEIVER COMPRISING A COMMAND SOURCE FOR PRODUCING A FIRST POLARITY OF CURRENT HAVING A MAGNITUDE PROPORTIONAL TO THE DESIRED WEIGHT OF MATERIAL, A WEIGHT SOURCE COUPLED TO SAID RECEIVER FOR PRODUCING A SECOND AND OPPOSITE POLARITY OF CURRENT HAVING A MAGNITUDE PROPORTIONAL TO THE WEIGHT OF MATERIAL SUPPLIED TO SAID RECEIVER, A TARE SOURCE FOR PRODUCING A CURRENT HAVING SAID FIRST POLARITY AND HAVING A VARIABLE MAGNITUDE AN OFFSET SOURCE FOR PRODUCING A CURRENT HAVING SAID SECOND POLARITY AND HAVING A MAGNITUDE PROPORTIONAL TO THE WEIGHT OF MATERIAL TO BE SUPPLIED AT SAID TRICKLE RATE, MEANS SELECTIVELY ENERGIZING SAID OFFSET SOURCE, A COMMON SUMMING JUNCTION COUPLED TO SAID COMMAND, WEIGHT, TARE, AND OFFSET SOURCES, MEANS COUPLED TO SAID JUNCTION FOR PRODUCING A CONTROL SIGNAL INDICATIVE OF THE RELATIVE MAGNITUDES OF SAID CURRENTS, MEANS COUPLED TO SAID PRODUCING MEANS AND TO SAID TARE SOURCE FOR CHANGING SAID TARE CURRENT TO A MAGNITUDE PROPORTIONAL TO THE TARE WEIGHT OF SAID RECEIVER, MEANS COUPLED TO SAID PRODUCING MEANS AND TO SAID MATERIAL SOURCE FOR SUPPLYING SAID MATERIAL AT SAID BULK RATE IN RESPONSE TO THE MAGNITUDE OF SAID FIRST POLARITY CURRENTS EXCEEDING MAGNITUDE OF SAID SECOND POLARITY CURRENTS, MEANS COUPLED TO SAID PRODUCING MEANS AND TO SAID OFFSET SOURCE FOR REMOVING SAID OFFSET CURRENT IN RESPONSE TO THE MAGNITUDE OF SAID SECOND POLARITY CURRENTS EXCEEDING THE MAGNITUDE OF SAID FIRST POLARITY CURRENTS, AND MEANS COUPLED TO SAID PRODUCING MEANS AND TO SAID MATERIAL SOURCE FOR SUPPLYING SAID MATERIAL AT SAID TRICKLE RATE IN RESPONSE TO THE REMOVAL OF SAID OFFSET CURRENT AND IN RESPONSE TO THE MAGNITUDE OF SAID FIRST POLARITY CURRENTS EXCEEDING THE MAGNITUDE OF SAID SECOND POLARITY CURRENT. 